Servomotor for vehicle brakes



NOV. 28, 1939. FITZGERALD SRVOMOTOR FOR VEHICLE BRAKES Filed June 15, 19:56

2 Sheets-Sheet 1 Nov. 28, 1939.

H. R FITZGERALD SERVOMOTOR FOR VEHICLE BRAKES 2 Sheets-Sheet 2 Filed June 13, 1956 INVENTOR.

#Heap E rzqfemp DJOEZWCL OF m n A Patented Nov. 28, 1939 UNITED STATES PATENT oFlicE saavomo'roa Foa VEHICLE BRAKES Harold R. l`itzgerald,\Rocky River, Ohio, assigner to The Midland Steel Products Company,

Cleveland, Ohio, a corporation of Ohio Application June 13, 1936, Serial No. 85,131

2 Claims.

'I'his invention relates to new and useful improvements in-vehicle brakes and an object of the invention is to provide a brake system including hydraulic brakes actuated either manually or by means of a vacuum eiiect derived from the power plant of the vehicle.

Another object of the invention is to providey employed to designate like parts throughout the several views, A

Fig. 1 is a sectional view partly in elevation of a brake system for actuating hydraulic brakes either manually or by means of vacuum,

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1,

Fig. 3 is a sectional view taken along the line 3-3 of Fig. A1,

Fig. 4 'is a sectional view partly in elevation of a brake system for actuating mechanical brakes either manually or by means of the effect of vacuum,

Fig. 5 is a sectional view corresponding to the line 5--5 of Fig. 4, and

Fig. 6 is a broken elevational view showing the connection of the power lever means and brake pedal lever to the brake cross shaft.

Referring to Figs. 1 through 3, the numeral I0 designates a vacuum suspended power cylinder suitably supported on the vehicle frame by means of a bracket II, and reciprocally mounted in the power cylinder is a piston I2 provided with a centrally disposed aperture for the reception of the rear end of a tubular piston rod I3 rigidly secured to the piston l2 by means of a nut I5. The front wall I6 of the power cylinder ls punched out to provide a hollow boss Il for the rigid reception oi a packing and bearing member yI8 extending a substantial distanceinto the power cylinder, and which slidably receives the tubular piston rod I3 in substantially fluid tight engagement. A ilexible boot 20 is attached to the bearing member I8 and to the forward end 2| of the piston rod I3 to further prevent the passage of air between the packing I8 and the plston rod I `3. i

The forward end of the tubular piston rod I3 5 is rigidly secured to a control valve 25 comprising a valve housing having an axial bore 26 communicating with the tubular piston rod I3, and with lateral, ports 21, 28 and 29. The port 21 communicates with the atmosphere through a 10 breather or air cleaner 30, and the port 28 is adapted to be connected with the intake manifold of an internal combustion engine for the source of suction or partial vacuum, while the port 29 is connected by means of a exible con- 15 duit 3| to the forward end 32 of the power cylinder I0. Y

Reciprocally mounted in the valve bore 26 is a piston type valve 3.5 having spaced apart annular closures or valve members 36 and 3l which 20 dene an annular recess 38 of suillcient length to at all times spanthe atmosphere port 2l. A spring 39 is yinterposed between the end of the valve 35 and a shoulder 40 formed by a reduced portion of the bore 26, and operates 25 to normally urge the piston valve 35 to brake release position, shown in Fig. I. When the piston valve 35 is in brake release position the front end 32 of the power cylinder communicates with the source of suction through the 30y ilexible conduit 3I, brake port 29, bore 26 and the manifold port 28, while the rear end 4I of the power cylinder is also connected to the source of suction through the tubular piston rod I3, bore 26 and the manifold port 28` to thereby 35 suspend the piston I2 in vacuum.

'I'he outer end of the piston valve 35 is provided with an axial cavity for the loose reception of one end of a valve rod 43 the opposite end of which is rigidly secured to a yoke 4'4 4d carried by a bushing 45 forming part of a lost motiondevice. A boot 46 has one end seated in a groove around the valve housing and the other end is disposed about the valve stem 43 to exclude extraneous matter from the bore 26. 45

The lost motion device and lever mechanism for operating the control valve comprises a brake pedal 50 at all times urged to brake'release position by a retractor spring 49 and is fulcrumed intermediate its ends about a pin 5I carried by 50 the vehicle and terminates at its upper end in a foot engaging pedal portion 52. lThe lower end 53 of the brake lever 56 carries-the bushing 45 provided with a bore 54 "in which is loosely disposed, as shown in Fig. 3, a pin 55 pivotall'y 55 has its side plates 58 journaled about the valve.

pin 55 and has its closed end disposed about'the tubular piston rod `I3 and is secured to the valve housing by means of the nut 59.

In order to connect the hydraulic master cylinder 69 with the power piston rod I3, the brake lever 58 is provided with an opening 6| for the loose reception of a pin 62 which is supported in the opening 6| by connection as at 63 with the power levers 56, and pivotally connected to the pin 62 is the .bifurcated end 64 of a piston rod 65 provided with a piston 66- disposed in the i hydraulic master cylinder 60. The master cylinconduit system 61 not completely shown whichleads to the wheel brake cylinders of the vehicle wheels.

From the foregoing it will be seen that the brake pedal 50 is actually a lever having a power arm 10 extending from the fulcrum point 5I to the foot engaging pedal 52, and a weight arm 1| extending from the fulcrum point 5| to the pin 55.

In operation, assume that the parts are in the position shown in Fig. 1, which corresponds to brake release position and the internal combustion engine is operating and creating partial pressure in the intake manifold of the vehicle engine. The piston I2 will be submerged in vacuum since the manifold-port 28 is in communication with the tubular piston rod I3 leading to the rear end 4|- of the power cylinder I9 and is in communication with the front end 32 of the power cylinder through the'i'lexible con-v duit 3|. When it is desired to apply the brakes, foot pressure is exerted on-the foot pedal 52 causing the brake lever 58 to swing counterclockwise about the fulcrum pin `5| and the weight arm 1| to move relative to the hydraulic pin 62 in the aperture 6| and the bushing 45 to move relative to the valve pin 55 which causes the piston valve 35 to move inwardly of the valve housing against the tension of the valve spring 39 to a position wherein the closure valve 31 interrupts communication between the brake port 29 and the manifold port 28 toslightly uncover the brake port 29 to establish communication between the atmosphere and the front end 32 of the power cylinder by way of the atmosphere port 21, annular recess 38, the partially uncovered brake port 29 and the flexible conduit 3| Since the lrear end 4I ofthe power cylinder is at all times in communication with the source of suction, the piston I2 is subject to a differential pressure which causes the piston I2, rigid conduit I3 and yoke 51 to move to-the right as viewed in Fig. l. This movement of the yoke 51 swings to the power levers 56 in a counterclockwise directionabout the fulcrum pin 5| to thereby move the hydraulic plunger 66 into the master cylinder 60 to distribute the brake iluid to the wheel brake cylinders and thus apply the brakes.

Movement of the tubular piston rod I3 and yoke 51 effects bodily movement of the control valve to the exclusion of movement between the valve 35 and the control valve housing due to the lost motion slot 54 in the brake pedal lever 58.

If pedal pressure on the brake lever 5l! is reduced the retractor spring Q9 swings the brake alarms? 'lever 58 in clockwise '35 to a lap position. wherein the valve closure 91 direction to move the valve covers the brake port 29 to thereby hold the brakes in applied position without additional exertion on the part of the operator. As soon as pressure on the foot pedal is' released. the 'valve spring 39 will move the valve from lap position to brake release position, whereupon the atmosphere will be cut oil and the iront end 32 of the power cylinder will be in communication with the source of suction permitting the piston I2 to be returned to normal position-and release 50, a greater portion of the brake port 29 will l be uncovered thereby permitting a more rapid entrance of atmosphere into th-front end 32 of the power cylinder with more severe application of the brakes.

Should differential pressure fail to be createdv in the power cylinder- I0 after initial movement of 'the brake pedal 58, the lost motion pin 62 will be in a position to immediately bottom in the slot 6| in the brake lever'so that further movement of the brake lever 50 will force the hydraulic plunger 66 into themaster cylinder 60 to apply the brakes solely by the physical force of the operator. A

From the foregoing it lwill be seen that the power lever means 56 which operates the hydraulic piston 66 has a power arm extending from the stud shaft or fulcrum pin 5| to the valve pin 55 and has a weight arm extending from the fulcrum pin 5| to the hydraulic lost motion pin 62.-

When the brakes are operated solely by the physical force of the operator the brake lever 58 has a power arm extending from the footl pedal 52 to the fulcrum pin 5I and has a weight arm extending from the fulcrum 5| to the hydraulic pin mechanical lever to operate the hydraulic piston 66 solely by the physical force of the operator.

Figs. 4 and 5 relate to a diil'erent embodiment of the invention and comprises an air suspended power cylinder supported on a vehicle by means of a bracket 8|, and is provided with an air cleaner 82 which at all times communicates the rear end 83 of the power cylinder with the atmosphere. The front wall 85 of the power cylinder is punched out to provide a hollow boss 86 for the reception of a packing and bearing member 81 in which is slidably mounted a piston rod 88 connected at one end lto a piston 89 disposed-in the power cylinder 80. 'A boot 90 is connected to the packing 81 and to the piston rod 88 to ins ure an air tight connection therebetween.

A control valve is rigidly secured to the piston rod 88 by means of a bracket 96 mounted on the piston rod 88 by means of pins 91. The

control valve -95 comprises a housing having an shaped valve ||0, they/al1 portion of which normally covers the vacuum port |03. The spaced apart valve members |09 and ||0 define an an nular recess which ycommunicates with spaced apertures ||2 in the bottom of the cup shaped valve H0. A valve spring ||3 is interposed between the closure valve and a shoulder formed by a reduction o f the bore `|00 and operates to normally urge the piston valve |08 to brake release posit-ion shown in Fig. 4. When the control' valve is' in brake release position the power piston 88 is suspended in air since the rearfend 83 of the power cylinder'communicates with the atmosphere through the breather 82 and theiront end ||4 of the power cylinder communicates with the atmosphere through the rigid conduit |04, bore |00. air port |02 and the breather |01.

The outer end of the piston valve |08 is provided with an axial cavity for the loose reception of one end of a valve rod H5 the opposite end of which is connected to a lever H6 of a lost mo- .l tion device hereinafter described. A boot ||1 has one end seated about the valve housing and the other end about the valve stem ||5 to exclude foreign matter from'the bore |00.

'I'he lost motion and lever mechanism for operating the control valve 85 comprises a pair oi supporting or carrier plates |20 rigidly connected vby the pins 81 to the piston rod 89 and carry a fulcrum pin |2| to pivotally support the lever 8 intermediate its end, the lower end |22 of which is pivotally connected by a pin |23 to one end of spaced links |24 having their opposite ends pivotedon a bushing |25 rigidly carried by an arm or projection |28 of a brake pedal lever 21 fulcrumed at its lower end about-a stub shaft |28 supported by the motor vehicle and the brake lever is provided at its opposite end with a foot engaging pedal |29. A retractor spring |30'urges the parts to brake release position shown in Fig. 4.

Power lever means for transmitting the operative movements of the power piston 88 to the brakes are provided and comprise a pair of spaced lever plates |35 pivotally connected to a pin |3| carried by the supporting plates |20 and are fulcrumed about the stub shaft |28. Each of the levers |35 have a pair of oppositely extending lever arms |38 and |31 Joined together at their outer ends by pins |38 and |39 which pivotallyI support a pair of spaced links |40 pivotally connected to a lever |42 rigidly secured at |43 to a tubular cross shaft |44 suitably journaled on the vehicle. The lever arms |31 of the power levers |35 may be disposed at such an angle with respect to the stub shaft |28 so as to place the pivot pin |39 intermediate the stub shaft |28 and the other pivot pin |3 Keyed to the cross shaft |44 are a pair of brake levers |45 each 'pivotally connected at their outer ends to brake cables |41 leading to the front and rear brakes of the vehicle.

In operation assume that the brake is in brake release position shown in Fig. 4 and the internal combustion engine is operating and creating partial pressure in the intake manifold of the ve- 2,161,115? resp-ect to the aperture |05 by means of a packing pressure will enter thel port |02 and rigid conl 3 hicle engine. The power piston Il is submerged in atmosphere since the valve air port |02 is in `communication with the rigid conduit |04 leading tothe front end i4 of th power cylinder, and the breather 82 exposes the rear end I3 ofA 5 the power cylinder .to the atmosphere. When it' is desired to apply the brakes by power, the operator slightly depresses the brake lever |21. This movement swings thebrake lever |21 about its fulcrum |28 and causes the brake arm |28 and l0 links |24 to move relatively to the lost motion pin |3|, due to thelarge diameter of the opening in the bushing |25 with respect to the lost motion pin |3|, whereby the valve lever ||8 will push the valve |08 inwardly of the valve housing l5 against the tension of the spring ||3 to close the atmosphere port |02 and slightly uncover the' v acuum porti03. This sets up a partial vacuum at the front end ||4 of the power cylinder 80 since the latter is now in communication Awith the 20 intake manifold by way of the vacuum port |03, bore |00. and rigid conduit |04. With atmosf pheric pressure on the opposite side of the piston 89, a differential pressure is exerted thereon and causes the piston 88 to moveto the left as 23 viewed in Fig. 4. This movement of the piston causes bodily movement of the supporting plates |20 and lost motion pin 3| with respect to the slot |30 in the brake pedal arm |28 and swings the power levers 35 in a counterciockwise di- 80 rection about the stud shaft |28 to thereby rotate the cross shaft |44 and cable levers |45 to effect braking movement of the brake cables I 41 to thus apply the brakes. Movement of the piston 88 and carrier plates |20 effects bodily move- 88 ment of the rigid conduit 04 with respect to the v power cylinder and also bodily movement of the control valve to the exclusion of any N movement between the valve |08v and the control valve housing due to' the lost motion slot |30 in n the brake arm |28.

If the foot pressure on the pedal |29 is reduced the retractor spring |30 swings the brake lever |21 in clockwise direction thereby'swinging the valve lever ||8 in counterclockwise direction to a move the valve ||0 to lap position wherein the valve |0 covers the vacuum port |03 and the atmosphere port |02 to thereby hold the brakes in applied position without additional exertion on the part lof the operator. As soon as pressureis removed from the foot pedal, the valve spring' ||3 moves the valve from lap position to brake release position shown in Fig. 4, whereupon the source of suction will be out oil and atmospheric 0I duit |04 and thence into the front end ||4 of the power cylinder permitting the piston therein to be returned to normal position and release the brakes under the normal action of the retractor spring |30.

In a brake application, it willI be seen that the greater pressure exerted on the foot pedal |28, a greater portion of the vacuum port |03 will be uncovered thereby permitting a more rapid creation of vacuum in the front end ||4 of the power cylinder with consequent more severe application of the brakes.

The manual operation of the brakes follows the power application so that should the source of suction fail the lost motion pin |3| is in a position to immediately bottom in the slot |30 in the brake arm |28 so that further movement of the brake lever |31 will swing the power levers |35 in a counterciockwise direction to operate the links |40 and lever |42 to manually operate the cross u shaft |45 and cable levers HB and consequently the wheel brakes through the cable i'l.

It will be understood that various changes in the construction and arrangement of parts may be resorted to without departing from the scope of the appended claims.

I claim:

1. In a, braking apparatus, brake applying mechanism, a power chamber having a pressure responsive member therein, a rod for said pressure responsive member and operable to effect operation of said brake applying mechanism, a valve housing mounted on said rod outside of said power chamber, a rigid conduit slidably disposed in an end wall of said power chamber and terminating a xed distance short of said pressure responsive member, a control valve in said valve housing for controlling communication of brake actuating fluid through said rigid conduit to said power chamber, and operator operated means for controlling operation of said control valve.

2. In a braking apparatus, brake applying mechanism, la power device having a pressure responsive device, a piston rod for said pressure responsive device operable to eect operation of said brake applying mechanism, a valve housing mounted on said piston rod outside of said power device, a rigid conduit slidably disposed in an end Wall of said power device and terminating ay fixed distance short of said pressure responsivel device, a control valve in said valve housing for controlling communication of the brake actuating uid through said rigid conduit to said power device, a valve operating lever mounted upon said rod, a foot. pedal, and means connecting the lever and pedal and having a. lost motion connection with said piston rod.

HAROLD R. FITZG.' 

